Neurodegeneration has proven notoriously difficult to study and there is currently no proven or acceptable method to prevent or slow down the course of disease in humans. A very successful intervention for Parkinson's disorder (PD) is neuromodulation via deep brain stimulation (DBS). DBS successfully restores motor function but what DBS does to the course of the disease is very poorly understood. Intriguingly, a few rodent model studies and clinical observations suggest that DBS could be neuroprotective, but because current practice is to implant the electrodes late in the progression of the disease, neuroprotective effects of electrical stimulation have been challenging to document. It is therefore vital that we are not missing on a crucial opportunity for neurological patients and research the causal links, mechanisms, and timelines associated with neuroprotection via neuromodulation. I propose an interdisciplinary approach for which I am uniquely trained that uses optogenetics, electrophysiology, biochemistry, and collaborative device engineering to study the interplay between neuronal health and brain circuit activity in intact behaving rodents. Specifically, I propose to study the factors influencing the function and health of dopaminergic neurons in the brain and their role in animal behavior. Our findings could allow us to positively interfere with cells such as the dopaminergic neurons in the substantia nigra pars compacta (SNc) that degenerate and die in PD. Below I list 3 specific challenges that I will tackle using innovative, interdisciplinary, approaches. 1. Are all SNc dopaminergic neurons equally impactful on behavior or are there hotspots where cells, due to their heterogeneous electrical and neurochemical characteristics and connectivity, can maximally interfere with behavior when degenerated? 2. Once dopaminergic degeneration starts, can neurodegeneration be halted or slowed down by altering the activity of defined brain circuits? I will test this intriguing hypotheis by performing chronic optogenetic control of inputs to the SNc and measure changes in the degeneration rate. 3. Is growth factor signaling directly contributing to dopaminergic neuroprotection and what are the timelines needed for neuroprotection? Previous experiments applied growth factors liberally in a non-specific fashion and/or with poor temporal resolution. I will develop optogenetic methods to achieve cell-type specific control of growth factor signaling so I can directly probe the protective role of growth factors in defined cell types, and especially cells prone to degeneration. These tools could also be applied to research beyond the nervous system since growth factor signaling is involved in key cellular phenomena such gene transcription that can impact the cell survival, differentiation, and function. Together these innovative projects will contribute to my long-term goals of building cellular resilience via neuromodulation and have a paradigm-shifting impact in neurodegeneration research.